Current News

Link Between Autism and Mental Retardation Lacks Data

A Willamette
University professor's recent article in the journal "Focus on
Autism and Other Developmental Disabilities" challenges the
long-held assumption that individuals with autism are mentally
retarded, a finding that could potentially change the way families
and schools across the country care for children with autism. The
finding is especially significant because autism is assuming
epidemic proportions, with the number of children diagnosed
increasing more than 20 percent each year according to the U.S.
Department of Health.

Meredyth Goldberg Edelson's findings, published in the Summer
2006 issue of "Focus," are expected to generate controversy, but
other peers back her up. When the journal decided to publish claims
that challenge 60 years of accepted assumptions, the editors
solicited two highly respected autism experts to respond.

"We anticipated strong reservations and were surprised that both
individuals commended Meredy for raising the question and for her
careful approach to analyzing the data," said Co-Editor Juane
Heflin. Both responses called for more extensive and objective
research.

"Although she is challenging the status quo, the quality of
Edelson's work is excellent," said Richard Simpson, professor of
special education at the University of Kansas and former editor of
the journal "Autism and Other Developmental Disabilities."

"There are so many claims and they're so widespread that no one
has bothered to look at the data behind the claims," said the
Willamette psychology professor. "Many claims are based on faulty
data or no data at all, and data that is available is 35 to 40
years old and based on measures that don't even measure
intelligence. No one had ever systematically analyzed the evidence
in support of those claims."

Edelson examined the autism research to determine whether these
claims were based on empirical data, what the quality of the data
is, and whether non-empirical claims could be traced to data. She
reviewed 215 studies (dating from 1937 to 2003) that made 223
claims about the rates of mental retardation in autism. Only 58 of
those claims were supported by data, 165 were made in the absence
of data, and 8 made both empirical and non-empirical claims. Newer
non-empirical claims cited older empirical claims, often based on
faulty measurements.

"Most researchers reported their results without describing how
they measured intelligence," Edelson said. "And the way
intelligence is measured varies widely, with nearly all of the
studies based on inappropriate measures. Some used development
measures or adaptive skills scales, which are not measures of
intelligence. Many times, if the researchers had a child they
couldn't test, they just assumed he or she was retarded and
assigned a low IQ score.

"Typical intelligence tests require children to have good verbal
skills, among other things, but since autism impairs a child's
ability to communicate with and relate to others, children with
autism don't perform well," she said.

In an earlier study, Edelson assessed children with the Test of
Non-verbal Intelligence (TONI), which involves abstract reasoning
and does not require a verbal response. Using the TONI, Edelson
found the children in the study had an average intelligence score
of approximately 90, which indicates average intelligence. Only 19
percent of Edelson's subjects scored in the mentally retarded
range. A second study conducted in Taiwan with children who were
even less verbal confirmed the earlier results.

"I'm not saying that children with autism are or are not
mentally retarded," Edelson said. "I'm just saying the literature
doesn't scientifically support the claims."

Because retardation in children with autism has been so widely
accepted, Edelson said schools and parents have lowered
expectations of this group. "In the 1950s, children with autism
were institutionalized," she said. "Today we know that they have
more options, from education and treatment to life plans including
college and careers, marriage and children. If most children with
autism aren't mentally retarded, we need to find ways for them to
interact with society and help them become all they can."

Edelson's Findings
Edelson's research indicated that most of the claims regarding the
rates of mental retardation (MR) in children with autism were not
based on empirical data.

Seventy-four percent of the articles that made claims about the
prevalence of MR in children with autism came from non-empirical
articles; only 26% derived from empirical studies.

Of the 165 non-empirical claims made, 36% never made a citation
in support of the claim; an additional 8% made a citation that did
not provide evidence to support the claim; and 21% claimed that a
higher percentage of children with autism were mentally retarded
than was claimed in the citation used to support the
percentage.

A total of 53% of the non-empirical articles making claims
about the prevalence of MR in children with autism never traced
back to an empirical source when the citation trail was followed
historically.

Nearly two-thirds of the empirical studies cited by authors of
non-empirical articles were published prior to 1980, yet nearly 77%
of all non-empirical claims have been published since 1980.

The results found that empirical studies utilizing
developmental measures or adaptive skills measures (that made
estimates of intelligence or that assumed that un-testable children
had MR, as was frequently done in the 1960s and 1970s) reported
average prevalence rates of 80.53% for MR in children with autism,
and studies that utilized none of the methods reported average
prevalence rates of 55.91% for MR in children with autism.

There were other difficulties with the empirical studies as
well. Given these findings, there does not appear to be good data
supporting the claims about high rates of MR in children with
autism.